I've been having this problem with my 86 F150 for months now. It feels like it's running out of gas constantly. At take off it spits and sputters and i have to feather the accelerator to get up to speed. I can be going along fine at 65, 75 mph until i have to get up even the slightest incline or accelerate and it sputters, dropping power. Lately it has completely lost power after running any distance and has to "rest" before rail fuel pump comes back to life. I've replaced the rail pump and filter, which did no good. I can rev it just fine but cant put any load on it without sputtering. I has an 89 which had a similar issue til I replaced the relay but I cant even find the relay on this model. It just keeps getting worse. Any advice would be helpful. Where to start diagnosis? Experience with this issue...? anybody... HelP!

 

Do you have dual tanks? There are pumps in the tanks also.

I don't think these trucks have a fuel rail test port, but check yours to make sure. It would be nice if you could rig in a fuel pressure gauge temporarily, tape it on the windshield and go for a test ride. It should stay in the neighborhood of 39 psi.

 

Yeah, It's only got one tank. It just loses power to the rail pump after it runs awhile. I let it sit and it comes back on... sorta. I've been having issues with them for a bit. I replaced the rail pump and filter but didn't help. My next move was going to be the tank pump as I can hear the rail pump come on when ignition is on. But concidering this latest addition to the problem wondering if it's not electrical as when it quits I can't hear the pump come on til it " rests". Thx for your imput!

 

So I replaced the fuel pump relay and it didn't help. I don't understand this one. Guess it's time to take it to a shop for diagnosis. aarrgh

 

Check the connections on the top of your fuel tank back together. the plastic connector (that holds the pins on the top of the sending unit) gets a little slack with age. just roll under the truck with a creeper and make sure the connections are tight. my 85 had that sputtering issue and it would just buck around everywhere until I fixed it

 

I will try that immediately. Thanks alot. It's usually the simple fix i seem to miss.

 

Might work for yours: clean the IAC! Worked wonders for me. i thought I had the bucking issue cleared up but it started up on the way to work again.

Just go get your regular auto parts store brand carb and throttle body cleaner. unplug cable, then unbolt your IAC from the throttle body and make sure the gasket is off. fill up the holes with cleaner. it might take a bit but fill it up all the way and set it aside for 10 min. go back with q tips and swab the insides and outside, get all the carbon off. rinse twice (or not) I just did to be extra clean.
Reinstall!
worked wonders for me. only cost about a buck50 in carb cleaner and 15 min